Cellulosic fibrous structures are a staple of everyday life. Cellulosic fibrous structures are used as consumer products such as paper towels, toilet tissue, and facial tissue.
Multiple lamina cellulosic fibrous structures are very well known in the art of consumer products. Such products are cellulosic fibrous structures having more than one, typically two, laminae superimposed in face-to-face relationship to form a laminate. Frequently these laminae are embossed for aesthetic reasons, to maintain the laminae in face-to-face relation as the laminate is used by the consumer, or to provide spacing between the laminae.
During the embossing process, the laminae are fed through a nip formed between juxtaposed axially parallel rolls. Discrete protuberances on these rolls compress like regions of each lamina into engagement and contacting relationship with the opposing lamina. The compressed regions of the laminae provide an aesthetic pattern and provide for joining of and maintaining the laminae in face-to-face contacting relationship.
Embossing is typically performed by one of two processes, knob-to-knob embossing, wherein protuberances on axially parallel rolls juxtaposed to form a nip therebetween are registered with protuberances on the opposing roll, and nested embossing where the protuberances of one roll mesh between the protuberances of the other roll. Examples of knob-to-knob embossing and nested embossing are illustrated in the prior art by U.S. Pat. Nos. 3,414,459 issued Dec. 3, 1968 to Wells and commonly assigned; 3,547,723 issued Dec. 15, 1970 to Gresham; 3,556,907 issued Jan. 19, 1971 to Nystrand; 3,708,366 issued Jan. 2, 1973 to Donnelly; 3,738,905 issued Jun. 12, 1973 to Thomas; 3,867,225 issued Feb. 18, 1975 to Nystrand and 4,483,728 issued Nov. 20, 1984 to Bauernfeind. Commonly assigned U.S. Pat. Des. 239,137 is Mar. 9, 1976 to Appleman illustrates an emboss pattern found on commercially successful paper toweling.
The consumer presented with an embossed cellulosic fibrous structure as a consumer product typically desires the product to have a high quality cloth-like appearance, to have a relatively thick caliper and to have an aesthetically pleasing pattern. All of these attributes must be provided without sacrificing the consumer products' other desired qualities of softness, absorbency, and bond strength between the laminae.
Different attempts have been made in the art to improve upon the embossments caused by the embossing processes. For example, attempts have been made in the art to provide embossed patterns having different depths, and asymmetric embossments. In some of these attempts, the asymmetric embossments have different orientations on each lamina of the consumer product. Other attempts have been made in the art to provide embossments having a certain size and representing a particular surface area of the embossed sheet. Yet other attempts in the art teach a particular angle, relative to the machine direction of manufacture, for the embossments. Examples of such attempts are illustrated in U.S. Pat. Nos. 4,320,162 issued Mar. 16, 1982 to Schulz, et al.; 4,659,608 issued Apr. 21, 1987 to Schulz and 4,921,034 issued May 1, 1990 to Burgess et al.
Other attempts have been made in the art to provide embossments having crests and depressions which are joined in a particular configuration, or which provide patterns corresponding to the apparatus used to manufacture the cellulosic fibrous structure. At least one attempt in the art teaches a particular apparatus having meshed protuberances which come within a very short distance of the opposite roll. Yet this arrangement produces merely the nested embossments discussed above. Examples of such attempts in the art include U.S. Pat. Nos. 3,940,529 issued Feb. 24, 1976 to Hepford, et al., 4,325,773 issued Apr. 20, 1982 to Schulz, and 4,487,796 issued Dec. 11, 1984 to Lloyd et al.
Still other attempts in the art teach particular sizes of the protuberances and recesses on the roll used to form the embossed cellulosic fibrous structure. One example of such an attempt is illustrated in U.S. Pat. No. 3,961,119 issued Jun. 1, 1976 to Thomas.
It is apparent from the foregoing attempts, that the resulting cellulosic fibrous structures are still made according to one of the two known basic processes--either knob-to-knob embossing or nested embossing. However, the cellulosic fibrous structures made according to either process encounter certain drawbacks, discussed below, when the cellulosic fibrous structures are used as a consumer product such as paper towels, toilet tissue, or facial tissue.
What is needed in the art is a different type of embossing process which gives the cellulosic fibrous structure a thicker -caliper and a quilted cloth-like appearance, so that the consumer is presented with a consumer product which has the appearance of quality and yet does not allow the laminae to readily separate during use.